Unlike traditional wireless system architectures which employ proprietary inter-network protocol and signalling, newer wireless systems are implementing an all-IP based core network using a “collapsed” architecture. For example, the collapsed architecture may combine the various components in the UMTS packet domain architecture or the CDMA packet domain architecture into a single network element, for example the broadband wireless router (BWR).
The BWR may incorporate the various functional components in the UMTS architecture, for example, Node B, radio network controller (RNC) serving general packet radio service (GPRS) support node (SGSN) function, and a home location register (HLR). Similarly, in the CDMA 2000 architecture, the BWR may incorporate a base station (BTS), base station controller (BSC), packet data serving node (PDSN) functions, as well as an Authentication Authorization Accounting (AAA) server. For example, Flarion Technologies Inc.'s Flash OFDM system uses a Flarion Radio Router to provide a collapsed architecture for an all-IP based network.
Compared to traditional wireless system architecture, the collapsed architecture model is more simplistic because it hides the various interfaces between different functions and provides visibility at the IP layer for the radio access network (RAN) for effective traffic conditioning and Quality of Service (QoS) control. However, to support voice over IP (VoIP) and multi-media services, additional functionality is needed in the collapsed model to accommodate call admission control and seamless voice and multimedia call handoff.
A simplistic approach for call admission control is “call counting”. In this approach, the broadband wireless router keeps track of the count of the calls in progress. This is adequate for networks in which only voice services are being offered. However, if Session Initiated Protocol (“SIP”) based multimedia services are being offered in addition to the VoIP services, merely keeping track of call count is not sufficient for effective and efficient call admission control. Other more comprehensive methods are needed to augment functionality. The call counting approach also assumes that any bottleneck is at the radio access layer, while the backhaul and the core network are considered as over-provisioned. Moreover, the call counting approach assumes that the softswitch and media gateways are not a limiting factor. These assumptions may not be true in a large-scale network, and may not be cost effective.
For example, one call counting method consists of counting until the number of calls being admitted reaches the maximum number of calls (N) that the radio router can handle, then denying new requests. A new call can only be admitted when one of the ongoing N calls terminates. Furthermore, this approach lacks the end-to-end visibility to the condition of the call or session path. Using the call counting approach, a new call can easily be admitted on the originating radio router but rejected by the terminating radio router.
Such an approach can be further improved by setting the counter dynamically taking into account the available bandwidth and the bandwidth requirements of the new session or call being presented to the system.